Phase Relations

A soil is a skeleton of solid grains with water and air in the voids between them. Set the volume of each and the page works out the phase relations: the masses, the moisture content, the void ratio, porosity and saturation, and the densities and unit weights, taking ρ_w = 1 g/cm³ and G_s = 2.7. The dry unit weight and moisture content then place the soil on a compaction chart, where no soil can lie above the no-air-voids line.

What you are seeing

• The volume column. The volumes of solid (brown), water (blue) and air (white), stacked to scale; its height is the total volume V.
• The compaction chart. Dry unit weight against moisture content. The dashed blue line is the no-air-voids line, γ_dry = gρ_wG_s/(1 + m_cG_s): the voids are full of water, S = 1. The black dot is the current soil; remove the air and it moves onto the line.
• Derived quantities. Every phase relation for the current volumes; the ? by each gives its definition.